Map Methods

Finally, we will implement a few utility methods from the Map interface that are useful for working with our MyHashMap.

entrySet Method

We might want to be able to iterate over every SimpleEntry<K, V> saved in the MyHashMap. Since these entries are unique and have no order (since keys have no order), we typically store the collection of SimpleEntry<K, V> as a Set. Implement a method:

public Set<SimpleEntry<K, V>> entrySet()

that:

  1. Creates a new empty HashSet<SimpleEntry<K, V>>

  2. Iterate over every LinkedList of the hashtable and add all of the SimpleEntry<K, V> entries from the current LinkedList to the HashSet using the HashSet’s addAll method.

  3. Return the HashSet

containsKey Method

A common method that is used with Maps within applications is deciding whether a given key is already stored in the Map. Implement a method

public boolean containsKey(K key)

that returns true if key is already contained in the MyHashMap, else false.

Hint

Our find helper method implemented in Part 2 should be really helpful again here.

containsValue Method

Another common method that is used with Maps within applications is deciding whether a given value is already stored in the Map. Implement a method

public boolean containsValue(V value)

that returns true if value is already contained in at least one in SimpleEntry<K, V> in the MyHashMap, else false.

Hint

Unfortunately, our find helper method is not helpful here. Instead, we should iterate over every SimpleEntry<K, V> in every LinkedList of the hashtable and return true if the getValue() of any SimpleEntry<K, V> equals() the given value.

Testing Our Progress

Do not forget to write unit tests verifying that your entrySet, containsKey and containsValue work as intended.

Committing Your Progress

Don’t forget to frequently save your progress to GitHub using the add/commit/push commands with git.